1. Field of the Invention
This invention relates to a film cartridge having a teremp along a film exit slit thereof and to a method of bonding the teremp to a shell plate of the film cartridge. This invention also relates to the teremp.
2. Description of the Prior Art
A photographic 35 mm roll film is accommodated in a film cartridge which basically comprises a tubular shell plate, a film spool, and caps on the ends of the shell plate. A light-shielding material generally called teremp is bonded on the inner surface of the shell plate along a film exit slit through which the film is drawn out. In this specification, the term "teremp" should be broadly interpreted to include both a material comprising a base fabric of a woven structure and pile provided thereon and a material comprising a base fabric of a knitted structure and pile provided thereon. As disclosed, for instance, in Japanese Unexamined Patent Publication No. 59(1984)-143841, a pair of teremps are bonded on opposite end portions of the shell plate before it is tubed.
In the method disclosed in U.S. Pat. Nos. 4,682,579 and 4,891,089, a teremp in a continuous length is conveyed in its longitudinal direction, bonded to the left and right end portions of the shell plate and then cut to conform to the shell plate. This method improves the teremp bonding efficiency as compared with a method in which the teremp is cut in advance to conform to the size of the shell plate and then bonded to the shell plate.
Recently there have come into wide use teremps of a knitted structure instead of teremps of a woven structure as disclosed in Japanese Utility Model Publication No. 61(1986)-34526. It has been found that the teremp of the knitted structure is more apt to be bonded in a wrong position than that of the woven structure. Our investigation has revealed that such a phenomenon is mainly due to the following two causes.
That is, in order to precisely bond the teremp to a predetermined portion of the shell plate (the portion which forms the film exit slit), a positioning member which contacts the teremp in continuous length while it is conveyed and positions it in the transverse direction is required. As such a positioning member, a member which contacts the teremp on its piled side is generally required for the reason of setting the teremp conveying path. An example of such a member is shown in FIG. 6 and indicated at 5a. In FIG. 6, reference numeral 21a denotes the teremp and reference numeral 21p denotes the piled side thereof.
Generally, the larger the angle .alpha. is, the more easily the teremp can be positioned, and accordingly, the angle .alpha. is formed substantially large. However when the angle .alpha. is large, a large drag acts on the piled side. The drag varies according to the orientation of the pile. In the conventional teremp of the knitting structure, the orientation of the pile is irregular and accordingly, the drag greatly fluctuates during conveyance of the teremp, whereby the teremp is displaced in a direction at an angle to the teremp conveying direction and as a result the teremp is bonded to the shell plate in a wrong position.
Further the teremp in a continuous length is formed by slitting a wide sheet in a continuous length. In the case of the teremp of the knitted structure, the teremp is slit by sealing and cutting in order to prevent fraying of the teremp and/or falling-off of the pile yarn at the cut portion.
However sealing and cutting often causes twist in the teremp in a continuous length. That is, the base fabric and the pile yarn of the teremp are generally formed thermoplastic fibers such as nylon or acetate, and thermoplastic resin such as polyvinyl resin or synthetic rubber resin is applied to the side of the base fabric opposite to the piled side as sealant or adhesive. The thermoplastic fibers and the thermoplastic resin at the cut portion expand due to heat applied thereto during sealing and cutting and solidify in that state while those in the middle portion are not subjected to heat, whereby twisting is generated in the teremp. When the teremp twists, the positioning member cannot precisely position the teremp relative to the shell plate and the teremp can be bonded in a wrong position.
Further twisting in the teremp can cause the teremp to slip off a conveyor roller.
When the teremp is bonded in a wrong position, light can enter the film cartridge to expose the film therein and/or the film therein can be damaged.
Further there has been a known a fact that a larger force is required to draw out the film in the film cartridge having the teremp of the knitted structure than in the film cartridge having the teremp of the woven structure.
There have been known various teremps. For example, in Japanese Utility Model Publication 46(1971)-20539, there is disclosed a teremp of a woven structure, and in Japanese Unexamined Patent Publication No. 54(1979)-36925, there is disclosed a teremp produced by static flocking.
However, the teremp of a woven structure is disadvantageous in that fraying is apt to occur and/or the pile is apt to fall off during manufacture thereof or when the film is drawn out or taken into the film cartridge. Further the teremp manufactured by the static flocking is disadvantageous in that the workability is bad since adhesive is used and the pile easily falls off though the manufacturing process is somewhat simplified.
Thus the assignee of the present invention has proposed a teremp which has a knitted structure as disclosed in Japanese Utility Model Publication No. 61(1986)-34526. Though the teremp of a knitted structure is advantageous over the conventional teremps in that fraying or falling-off of the pile is reduced, the light-shielding performance is sometimes unsatisfactory due to large spaces between the chain yarns.
Further since the pile yarns are knitted into the chain yarns of the base fabric, pile yarns easily fall off when the chain yarn breaks.
Further there has been proposed, as disclosed in Japanese Patent Publication No. 62(1987)-40696, a teremp having pile conductive fibers formed by dispersing linear polymer containing therein inorganic conductive material in fiber-forming polymer. However this teremp is apt to scratch the photosensitive layer of the photographic film due to its high rigidity and is expensive.
Further, there has been proposed in Japanese Unexamined Patent Publication No. 60(1985)-208751 a teremp formed of conjugated yarn. This teremp is disadvantageous in that it is expensive and at the same time, a large drag is generated when the film is drawn out the film cartridge due to large thickness of filaments.
Accordingly there has been a great demand for a teremp which can be manufactured at low cost and exhibits an excellent light-shielding performance and in which fraying or falling-off of the pile is less apt to occur.